From: Liam Howlett <liam.howlett@xxxxxxxxxx> Subject: mm: add vma_lookup(), update find_vma_intersection() comments Patch series "mm: Add vma_lookup()", v2. Many places in the kernel use find_vma() to get a vma and then check the start address of the vma to ensure the next vma was not returned. Other places use the find_vma_intersection() call with add, addr + 1 as the range; looking for just the vma at a specific address. The third use of find_vma() is by developers who do not know that the function starts searching at the provided address upwards for the next vma. This results in a bug that is often overlooked for a long time. Adding the new vma_lookup() function will allow for cleaner code by removing the find_vma() calls which check limits, making find_vma_intersection() calls of a single address to be shorter, and potentially reduce the incorrect uses of find_vma(). This patch (of 22): Many places in the kernel use find_vma() to get a vma and then check the start address of the vma to ensure the next vma was not returned. Other places use the find_vma_intersection() call with add, addr + 1 as the range; looking for just the vma at a specific address. The third use of find_vma() is by developers who do not know that the function starts searching at the provided address upwards for the next vma. This results in a bug that is often overlooked for a long time. Adding the new vma_lookup() function will allow for cleaner code by removing the find_vma() calls which check limits, making find_vma_intersection() calls of a single address to be shorter, and potentially reduce the incorrect uses of find_vma(). Also change find_vma_intersection() comments and declaration to be of the correct length and add kernel documentation style comment. Link: https://lkml.kernel.org/r/20210521174745.2219620-1-Liam.Howlett@xxxxxxxxxx Link: https://lkml.kernel.org/r/20210521174745.2219620-2-Liam.Howlett@xxxxxxxxxx Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Reviewed-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Davidlohr Bueso <dbueso@xxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 36 ++++++++++++++++++++++++++++++++---- 1 file changed, 32 insertions(+), 4 deletions(-) --- a/include/linux/mm.h~mm-add-vma_lookup-update-find_vma_intersection-comments +++ a/include/linux/mm.h @@ -2676,17 +2676,45 @@ extern struct vm_area_struct * find_vma( extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr, struct vm_area_struct **pprev); -/* Look up the first VMA which intersects the interval start_addr..end_addr-1, - NULL if none. Assume start_addr < end_addr. */ -static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr) +/** + * find_vma_intersection() - Look up the first VMA which intersects the interval + * @mm: The process address space. + * @start_addr: The inclusive start user address. + * @end_addr: The exclusive end user address. + * + * Returns: The first VMA within the provided range, %NULL otherwise. Assumes + * start_addr < end_addr. + */ +static inline +struct vm_area_struct *find_vma_intersection(struct mm_struct *mm, + unsigned long start_addr, + unsigned long end_addr) { - struct vm_area_struct * vma = find_vma(mm,start_addr); + struct vm_area_struct *vma = find_vma(mm, start_addr); if (vma && end_addr <= vma->vm_start) vma = NULL; return vma; } +/** + * vma_lookup() - Find a VMA at a specific address + * @mm: The process address space. + * @addr: The user address. + * + * Return: The vm_area_struct at the given address, %NULL otherwise. + */ +static inline +struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr) +{ + struct vm_area_struct *vma = find_vma(mm, addr); + + if (vma && addr < vma->vm_start) + vma = NULL; + + return vma; +} + static inline unsigned long vm_start_gap(struct vm_area_struct *vma) { unsigned long vm_start = vma->vm_start; _
